section 10
10
metal casting
Foundry operations use extremely high temperature processes and
produce large amounts of toxic dust.
Many of the hazards of this work are not immediately obvious. The
effects may not be noticed until many years later. It is important that
people working in metal casting understand the particular hazards
that their work involves.
The processes used in metal casting are very noisy, so there is also a
risk of noise-induced hearing loss.
This section covers hazards associated with:
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heat
•
dust and fumes
•
metal splashes and water explosions
•
refractory failure
•
material handling and storage
•
fettling.
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stop
The first line of defence is knowing what you are doing!
If you haven’t been trained for a particular task or equipment – STOP!
10.1 Heat
hazards
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Molten metal gives off extreme heat that can burn a
person by radiation or direct contact.
Molten metal or slag can severely burn workers.
Visible white-hot metal produces infrared and ultra-violet
radiation that can damage eyes and cause cataracts.
Specific sections of the foundry can be extremely hot.
Workers in very hot environments can easily become
dehydrated, stressed and fatigued. New workers may
find it takes a while to get used to working in the heat.
Water mixed with molten metal can cause an explosion.
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action
points
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Personal protective clothing
may enable you to walk away
from catastrophic incidents
that would otherwise severely
burn or kill you.
Always wear flameproof safety gear over your
overalls while doing:
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charging
–
tapping
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pouring
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casting operations.
This extreme temperature protection will
include:
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safety goggles/glasses
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face shield
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hard hat
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jacket
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apron
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gloves
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leggings
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heat-resistant safety boots that have suitable soles for the surface being
worked on.
Remember to wear ear protection!
You must wear natural fibre garments under
the overalls as many synthetic fabrics can melt
or catch fire. Generally, woollen garments are
preferred (even in hot climates!).
Keep your distance. Don’t stand any closer to
the molten metal than you have to.
Keep behind the barriers.
No-go zones must be administered and entry to danger zones must be kept to the
absolute minimum (e.g. when tapping cupolas).
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Make sure access to safety showers is kept clear.
Under no conditions should untrained persons or
visitors be allowed entry to no-go zones. The only
people who should be in the hot work area are those
who have been trained and are needed there to do
the work.
Workers must maintain their intake of water during
the day. The recommended intake is 1-2 litres per day.
REMEMBER to keep water away from molten
metal!
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10.2 Dust and fumes
hazards
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•
•
•
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•
Furnaces are full of toxic residues that can be hazardous. Carbon monoxide,
cancer-causing fumes, and isocyanides are all extremely dangerous. These are all
by-products of the foundry process.
The fumes, gases and particulates can be hazardous.
Foundries produce large quantities of hazardous/toxic waste. This can expose
the public to hazards if it is not controlled. This waste must be stored in a
remote location (never near any public areas).
Chemicals and solvents used in the pattern and
mould making processes are toxic. Section 2.6 of
these Guidelines provides more details on this.
Breathing in metal fumes and oxides can lead to
the flu-like illness metal fume fever quite suddenly.
Carbon monoxide may leak from furnace
charging doors. It is odourless and invisible but
can be deadly.
An enormous amount of dust is produced throughout the process. This dust
can give rise to silicosis, occupational cancers, occupational asthma and other
respiratory diseases that can be fatal.
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Remove or separate the hazard
(dust and fumes)
•
•
Make sure extraction fans are operating before
starting work.
Wherever possible separate workers from the areas
where fumes and dusts are present, by use of screens,
barriers, feed conveyors and local exhaust and
ventilation systems.
Monitor the hazard
•
•
•
Ensure that monitoring of exposure levels and times is
always done. Personal dosimetry will help to monitor
individual exposure.
Always study the Material Safety Data Sheet to identify
the potential hazards of each particular product being
used. Make sure that the MSDS is current.
Ensure that workers understand the MSDS (many are
written for a technical audience).
Reduce the exposure to the hazards
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Wear respirators:
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around furnaces
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when working with, or maintaining, the furnace
refractory
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when making moulds (especially if toxic or dusty
substances are being used)
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during breakout and fettling procedures.
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Seek expert advice to help you select the best
respirators for your environment:
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The minimum requirement is normally halfface respirators fitted with particulate and
gas cartridges, but in some cases FPBRs (Fan
supplied, Positive pressure, Breath-responsive
Respirators) may be more suitable.
–
Wear respirators when exposure monitoring
shows that you should. Make sure the
respirator is compatible with your other safety
equipment.
Keep breathing apparatus and resuscitation
equipment maintained and ready for use.
Regularly clean or exchange your respirators.
When people have to wear respirators, employers
must put systems in place to make sure they are
providing proper protection. These include:
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worker training
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monitoring programmes
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medical screening
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cleaning processes
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provision for storage
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regular maintenance programmes
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inspection schedules.
Clean dust away with high-powered industrial
vacuum cleaners.
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10.3 Metal splashes and water
explosions
hazards
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•
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Water and molten metal do not mix!
Dropping wet items into a furnace can cause an
explosion.
Dropping large pieces of metal into furnaces can
cause splashes or explosions.
Water inside containers can also cause
explosions if the container is dropped into
a hot, empty furnace. The container can be
thrown out of the furnace and may cause
serious injury.
Spill pits can collect moisture. In the case of a
run-out or emergency dumping, the contact of
the molten metal with this water can lead to an explosion.
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Never feed damp or wet scrap into containers.
Keep scrap dry! Store undercover if possible for 48
hours prior to using for charging and check it is dry
before using it.
Keep spill pits dry.
Don’t drop large or heavy pieces into furnaces or
crucibles. Cut large pieces down to smaller bits
if necessary.
Take extreme care to prevent slag coming into contact
with water.
Make sure that the ladle and other parts that will be
in contact with molten metal are dry before metal is
poured into them.
Keep areas around furnaces dry. If they are wet, dry
off the area and dispose of damp materials before
starting work.
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10.4 Refractory failure
Containers for molten metal are made from heat-resistant (refractory) materials. These are usually
ceramic (brick like) and brittle. With time and heavy use, they can wear or crack, allowing the
molten metal to leak out, creating a serious hazard called “refractory failure”.
hazards
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Refractory failure can lead to “run-out”. This can lead
to splatter or explosion.
Throwing heavy items into the furnace can damage
the refractory.
Bridging occurs when cold charge material is “hung
up” and not in contact with molten metal. The small
volume of molten metal in the furnace can superheat
rapidly. This can lead to refractory failure and a “runout” (escape) of the molten material.
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action
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Obey the following rules for your refractory:
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Treat it carefully.
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Check for cracks before each start-up.
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Do not use it if is damaged or excessive wear is
observed.
Don’t “drop” heavy items into a furnace.
Cut charge material to small sizes.
Preheat tools and charge material before injection into
the furnace if possible.
Be aware of the signs of bridging:
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Slow melt.
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Cold charge metal not falling into the furnace as expected.
If bridging occurs – shut the power off immediately!
Wait until the metal has cooled to a safe level before starting clean-up work.
Keep your refractory in good condition and well maintained.
Sampling must be taken in full heat protection PPE and must be done only by a
fully trained and competent person.
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10.5 Fettling
hazards
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•
•
The repetitive nature of the task of fettling can give rise to gradual process
injuries including muscle and joint damage.
This can also be an extremely dusty job and the dust created can be hazardous if
it is breathed in.
The grinding and cutting involved means this is extremely noisy work that will
damage hearing.
action
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Make sure you have the extraction system running
and that it is adequate for the work being done.
Wear the correct type of respiratory equipment.
Rotate work with other workers.
Regularly change your position and technique if
possible.
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10.6 Material handling
hazards
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•
Raw materials are heavy, so if they fall they will
injure you,
You can injure your back or other muscles when
lifting heavy materials and products.
action
points
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•
•
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Raw materials must be stacked properly so they
don’t fall.
Use lifting equipment to handle heavy materials or
products. Refer to section 4 of these Guidelines.
Do not attempt to lift heavy materials or products manually.
People working around overhead cranes, gantries or other work must wear a
safety helmet and must make sure they don’t walk under loads.
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10.7 Electrical safety
hazards
•
Induction furnaces are fed by extremely high voltages
that can easily electrocute and kill!
action
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Make sure the ground leak detector system is operating and checked frequently.
Power should be turned off as a precaution during slagging, sampling and measuring.
Never remove guards or panels over electrical gear.
Never by-pass interlocks.
Only qualified electricians must be allowed to maintain the equipment.
Only trained operators must operate induction electrical systems
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10.8 general safety
action
points
•
If maintenance work is required inside the furnace, the procedure for a confined
space (see section 3.2) must be followed.
Make sure charging platforms are unobstructed, level, well treaded, non-slip
and clean.
Broken moulds and rough castings often have sharp edges that can cut you.
•
•
!
employer’s
responsibilities:
Employers need to:
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•
•
•
•
•
insist on thorough and regular cleaning
make sure extraction ducts and fans are kept clean
have a refractory monitoring programme in place to ensure the risk of failure
of the refractory is minimised
make sure induction equipment is clearly marked with HIGH VOLTAGE signs
ensure systems are in place to protect workers against overexposure to
extreme heat
insist that workers wear Personal Protective Equipment that complies with
AS/NZS 1715 and 1716
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!
employer’s
responsibilities:
Employers need to:
•
•
•
•
have a regular programme for monitoring workers’ exposure to hazardous
substances
make sure no-go zones are clearly defined
have safety showers located in an area that is easily accessible from areas
where hot work is being carried out. Ensure these are regularly tested
provide mechanical lifting devices e.g. cranes and forklifts and ensure that
workers use them.
more information:
Further information:
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•
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Health and Safety Guidelines on the Management of Hazards in the Metal
Casting Industry – available from www.dol.govt.nz.
AS/NZS 1716:2003 Respiratory protective devices.
AS/NZS 1715:1994 Selection, use and maintenance of respiratory protective
devices.
Guidelines for Handling Molten Aluminum. Washington DC, The Aluminum
Association Inc, 2002.
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